Process of hydrocracking heavy oil

ABSTRACT

To provide a process of hydrocracking heavy oil capable of obtaining cracked light oil with higher yields and/or milder reaction conditions than the conventionally proposed hydrocracking process in a suspended bed method using an iron-based catalyst when hydrocracking heavy oil containing heavy metal components produced in a refining process of crude oil into lighter oil. 
     There are provided (1) a process of hydrocracking heavy oil containing heavy metal components produced in a refining process of crude oil, comprising a vacuum distillation step to obtain the heavy oil as distillation residue by vacuum distillation; and a reaction step to hydrocrack the heavy oil in the presence of an iron-based catalyst in a suspended bed reactor, wherein the distillation is conducted at 350° C. or less in the vacuum distillation step, (2) in the preceding process, reaction conditions in the reaction step are a reaction pressure of 60-160 kg/cm 2 ; a reaction temperature of 430-455° C.; and a reaction time of 30-180 minutes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention belongs to the technical field relating to a process of hydrocracking heavy oil, specifically relates to a process of hydrocracking heavy oil containing heavy metal components produced in a refining process of crude oil (hereinafter also referred to as petroleum heavy oil containing heavy metal components). In particular, the present invention belongs to the technical field relating to a process in which petroleum heavy oil containing heavy metal components such as vacuum residue is hydrogenerated in the presence of catalyst to obtain highly decomposed products.

2. Description of the Related Art

In the background of rapid changes in demand structure in which supply of heavier crude oil and demand for lighter products proceed simultaneously, an attention has been drawn to decomposition techniques of heavy oil for producing lighter products in short supply from excess heavy oil, as the limited reserves of petroleum inevitably diminish, its importance is increasing more than ever.

A lot of processes for thermal cracking and hydrocracking of heavy oil have been proposed. However, these processes have problems of some kind for hydrocracking heavy oil containing heavy metal components such as vacuum residues.

In more detail, such heavy oil contain a large amount of nitrogen compounds and sulfur compounds therein. In the case where decomposition of heavy oil are conducted in the presence of catalyst, a large amount of organometallic impurities hazardous to the catalyst is contained. As organometallic impurities (hereinafter also referred to as metal impurities), although the ones containing nickel (Ni) or vanadium (V) are most popular, there are some that contain other metals. These metal impurities are chemically bounded to organic compounds with relatively high molecular weight such as asphaltene in heavy oil. If they are present, catalytic activities for decomposition and removal of compounds containing nitrogen, sulfur and oxygen are markedly hindered.

As a method for treating the heavy oil without using catalyst, there is a thermal cracking process. So called coker process is known. The process poses a problem on treatment of a large amount of coke produced as by-product. Also, the yield of distillate oil obtained is inevitably lowered due to increase in gas generation resulting from overcracking. In addition thereto, it has drawbacks that there are a lot of aromatic and olefinic components, resulting in poor quality.

In a hydrocracking process in a fixed bed method by filling granular catalysts in a reactor, in the case of being highly decomposed, cokes as by-product and heavy metal components are gradually deposited on catalyst layers while being influenced by asphaltene and heavy metal components such as V and Ni in feedstock as mentioned above. As a result, there is a limit for a long-period continuous operation, causing the lowering of catalytic activity and clogging of catalyst layer.

In a hydrocracking process in a reactor of ebullated bed method using extrusion-molded granular catalysts of Co—Mo type and the like, there is no pressure-drop increase problem due to accumulation of coke etc. because of an intensive mixing state inside the ebullated bed reactor. Also, it has an advantage over a fixed bed method because a continuous operation can be done for a long period while keeping the catalytic activity constant by being capable of charging and discharging catalysts in operation. The operation, however, is more difficult than a fixed bed method because the catalyst is circulated in operation. The catalyst is expensive, the reaction pressure is generally as high as 150-200 kg/cm² (15-20 MPaG), and desulfurization and denitrogenation of reaction products are insufficient.

As an improving technique to solve the conventional drawbacks described above, there has been proposed a process in which petroleum heavy oil containing heavy metal components are supplied together with an inexpensive iron-based catalyst on a throw-away basis into a suspended bed (slurry bed) reactor for hydrocracking. Such a process (hereinafter also referred to as a hydrocracking process in a suspended bed method using an iron-based catalyst) is, for example, described in Japanese Unexamined Patent Publication No. 2001-89772.

-   [Patent Document 1]Japanese Unexamined Patent Publication No.     2001-89772

DISCLOSURE OF INVENTION [Technical Problems to be Solved]

In this way, there has been proposed a hydrocracking process in a suspended bed method using an iron-based catalyst, even in this process, however, further economical improvement is being desired.

BRIEF SUMMARY OF THE INVENTION

The present invention has been accomplished in such a situation above mentioned, and its object is to provide a process of hydrocracking heavy oil, which is capable of obtaining decomposed oil with higher yields and/or milder reaction conditions than the conventionally proposed hydrocracking process in a suspended bed method using an iron-based catalyst when hydrocracking petroleum heavy oil containing heavy metal components into lighter oil.

The above objects can be achieved by a process of hydrocracking heavy oil containing heavy metal components produced in a refining process of crude oil, comprising:

a vacuum distillation step to obtain the heavy oil as distillation residue by vacuum distillation; and

a reaction step to hydrocrack the heavy oil in the presence of an iron-based catalyst in a suspended bed reactor,

wherein the distillation is conducted at 350° C. or less in the vacuum distillation step.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing showing an example of embodiment of process of hydrocracking heavy oil containing heavy metal components according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have earnestly studied to achieve the foregoing object and accomplished the present invention. According to the present invention, the above object can be achieved.

The present invention thus accomplished pertains to a process of hydrocracking heavy oil, and is specified to the process of hydrocracking heavy oil according to Claims 1 to 8 in CLAIMS (the process of hydrocracking heavy oil in the first through the eighth inventions), which is based on the following constituent.

A process of hydrocracking heavy oil of Claim 1 is a process of hydrocracking heavy oil containing heavy metal components produced in a refining process of crude oil, comprising:

a vacuum distillation step to obtain the heavy oil as distillation residue by vacuum distillation; and

a reaction step to hydrocrack the heavy oil in the presence of an iron-based catalyst in a suspended bed reactor,

wherein the distillation is conducted at 350° C. or less in the vacuum distillation step (the first invention).

A process of hydrocracking heavy oil of Claim 2 is the process of hydrocracking heavy oil according to Claim 1, comprising: a recycling step in which a liquid-phase fluid obtained by gas-liquid separation of the reaction products from the reaction step is recycled to the suspended bed reactor; and

a recycling step in which after separation of a solid component from the liquid-phase fluid, the resultant fluid is recycled to the suspended bed reactor (the second invention).

A process of hydrocracking heavy oil of Claim 3 is the process of hydrocracking heavy oil according to Claim 2, wherein the content of heavy oil components with a boiling point of 525° C. or more in the liquid-phase fluid recycling in the recycling step is 10-100 mass % of the amount of heavy oil supplied into the suspended bed reactor in the reaction step (the third invention).

A process of hydrocracking heavy oil of Claim 4 is the process of hydrocracking heavy oil according to any one of Claims 1 to 3, wherein the reaction conditions in the reaction step are a reaction pressure of 60-160 kg/cm²; a reaction temperature of 430-455° C.; and a reaction time of 30-180 minutes (the fourth invention).

A process of hydrocracking heavy oil of Claim 5 is the process of hydrocracking heavy oil according to any one of Claims 1 to 4, wherein the iron based catalyst is a natural limonite iron ore catalyst (the fifth invention).

A process of hydrocracking heavy oil of Claim 6 is the process of hydrocracking heavy oil according to any one of Claims 1 to 5, wherein the iron based catalyst is a natural limonite iron ore catalyst of 2 μm or less in an average particle size being mechanically pulverized in a petroleum solvent (the sixth invention).

A process of hydrocracking heavy oil of Claim 7 is the process of hydrocracking heavy oil according to Claim 5 or Claim 6, wherein the natural limonite iron ore catalyst is a natural limonite iron ore catalyst containing essentially no iron oxide (the seventh invention).

A process of hydrocracking heavy oil of Claim 8 is the process of hydrocracking heavy oil according to any one of Claims 5 to 7, wherein on supplying the natural limonite iron ore catalyst into the suspended bed reactor, the amount supplied is 0.3-2 mass % as an ion component of the amount of heavy oil supplied (the eighth invention).

EFFECT OF THE INVENTION

The process of hydrocracking heavy oil of the present invention makes it possible to give decomposed oil with higher yields and/or milder reaction conditions than the conventionally proposed hydrocracking process in a suspended bed method using an iron-based catalyst when hydrocracking petroleum heavy oil containing heavy metal components produced in a refining process of crude oil into lighter oil.

BEST MODE FOR CARRYING OUT THE INVENTION

In an oil refinery, generally, crude oil is fed to an atmospheric distillation tower to separate it into oil fractions such as naphtha, kerosene and diesel, as well as atmospheric residue, which is discharged from the under-part of the atmospheric distillation tower, and the atmospheric residue is fed to a vacuum distillation tower. In the vacuum distillation tower, vacuum gas oil fraction is mainly collected. Simultaneously, vacuum residue is discharged from the under-part of the vacuum distillation tower, which is further decomposed in a thermal cracking process (coker process) or a hydrocracking process to produce naphtha, kerosene, diesel and vacuum gas oil fractions.

The present inventors have found that upon hydrocracking vacuum residue by a hydrocracking process in a suspended bed method using an iron-based catalyst, the use of vacuum residue cut by higher vacuum distillation temperature yields a low decomposition ratio, and the decomposition ratio tends to decrease with increase in vacuum distillation temperature. In the case of using vacuum residue obtained in a high vacuum distillation temperature, it is necessary to adopt severe conditions such as higher pressure and longer reaction time in the reaction step of hydrocracking, which leads to high plant costs.

In contrast, in the case of using vacuum residue obtained in a low vacuum distillation temperature, the decomposition ratio becomes high, and the decomposition ratio increases with decrease in vacuum distillation temperature. Specifically, it has been found that it is preferable to set a maximum temperature at 350° C. or less in a vacuum distillation tower, thereby the decomposition ratio becomes sufficiently high upon hydrocracking when this vacuum residue drawn off from the under-part of vacuum distillation tower is used. When the decomposition ratio becomes sufficiently high in this way, it becomes possible to obtain decomposed oil with high yield, and also decomposed oil with a satisfying yield in mild reaction conditions in a reaction step of hydrocracking. Namely, it is possible to obtain decomposed oil by hydrocracking in a higher yield and/or milder reaction conditions than the conventionally proposed hydrocracking process in a suspended bed method using an iron-based catalyst.

Therefore, the process of hydrocracking heavy oil of the present invention is a process of hydrocracking heavy oil containing heavy metal components produced in a refining process of crude oil, comprising:

a vacuum distillation step to obtain the heavy oil as distillation residue by vacuum distillation; and

a reaction step to hydrocrack the heavy oil in the presence of an iron-based catalyst in a suspended bed reactor,

wherein the distillation is conducted at 350° C. or less in the vacuum distillation step.

According to the process of hydrocracking heavy oil of the present invention, as is clear from the foregoing founding, the decomposition ratio becomes sufficiently high upon hydrocracking vacuum residue, so that it is possible to obtain decomposed oil in a higher yield and/or milder reaction conditions than the conventionally proposed hydrocracking process in a suspended bed method using an iron-based catalyst.

It is preferable in the process of hydrocracking heavy oil of the present invention to have a recycling step in which a liquid-phase fluid (hereinafter also referred to as liquid-phase fluid a) is obtained by gas-liquid separation of the reaction products obtained from a hydrocracking reaction step in a suspended bed reactor (hereinafter also hydrocracking reaction step), and after separation of a solid component from the liquid-phase fluid a, the resultant liquid-phase fluid (hereinafter also referred to as liquid-phase fluid b) is recycled into the suspended bed reactor (the second invention). It also preferable to have a recycling step in which the liquid-phase fluid a is recycled into the suspended reactor. The reason is as follows. Both the liquid-phase fluid a and the liquid-phase fluid b contain a heavy oil component (heavy residue) with a boiling point of 525° C. or more (+525° C.). By recycling them to the suspended bed reactor, re-decomposition of the heavy oil components takes place, a yield of oil fraction (C5-525° C.) is improved. Main difference between the liquid-phase fluid a and the liquid-phase fluid b is that liquid-phase fluid a contains a catalyst component, whereas liquid-phase fluid b hardly contains a catalyst component.

It is preferable that the content of heavy oil components with a boiling point of 525° C. or more in the liquid-phase fluid recycling in the above recycling step is 10-100 mass % of the amount of petroleum heavy oil supplied into the suspended bed reactor in the reaction step (the third invention). The reason is as follows. When the content of heavy oil components with a boiling point of 525° C. or more is less than 10 mass %, a yield of oil fraction (C5-525° C.) is hardly improved, and a bottom recycling effect cannot be displayed. On the other hand, when the content of heavy oil components with a boiling point of 525° C. or more is more than 100 mass %, although a yield of oil fraction (C5-525° C.) is remarkably enhanced, the rate of increase in the yield of oil fraction (C5-525° C.) is lower than that in the above-mentioned content of heavy oil components with a boiling point of 525° C. or more of 10-100 mass %, and the recycling efficiency is lowered.

Reaction conditions in the above reaction step, namely, the reaction conditions in a suspended bed reactor are not particularly limited, for example, they are set to be a reaction pressure of 60-160 kg/cm²; a reaction temperature of 430-455° C.; and a reaction time of 30-180 minutes (the fourth invention). The severer the conditions (higher reaction pressure, longer the reaction time), the higher the yield (conversion rate of residue, yield of oil fraction (C5-525° C.) is. In the present invention, however, milder conditions such as pressure of 60-120 kg/cm², temperature of 430-455° C. and time of 30-120 minutes can be adopted to give sufficient yield. The condition for providing hydrogen is generally 1 to 8 mass % although depending on flow of freedstocks.

In the process of hydrocracking heavy oil of the present invention, a natural limonite iron ore catalyst is preferably used as an iron-based catalyst (the fifth invention). The reason is as follows. Such a natural limonite iron ore catalyst has higher activities than iron-based catalysts such as Fe₂O₃ (hematite), FeS₂ (pyrite), FeSO₄ (iron sulfate), and is an inexpensive, natural catalyst being mined.

As a natural limonite iron ore catalyst, it is preferable to use a natural limonite iron ore catalyst of 2 μm or less in an average particle size being mechanically pulverized in a petroleum solvent (the sixth invention). The reason is that such catalyst has an excellent catalytic activity. The average particle size of limonite iron ore catalyst, for example, can be determined in the following method. Limonite iron ore catalyst is pulverized in oil by a ball mill and the like. The particle size of the catalyst thus pulverized is measured by a laser diffraction type particle size distribution analyzer. As a dispersion solvent for the analyzer, ethanol, isopropyl alcohol and the like are used. A sample (a mixture of oil and the above pulverized catalyst) is put into the solvent. Then, a 50% particle size (Dp50) is read out from a particle size distribution curve (particle size vs. mass % integrated value) outputted by the analyzer. The 50% particle size is defined as an average particle size.

It is preferable to use a natural limonite iron ore catalyst containing essentially no iron oxide (the seventh invention). The reason is that such catalyst has an excellent catalytic activity. Essentially no iron oxide means the content of Fe₂O₃ of 10% or less.

When the heavy oil is hydrocracked in the presence of an iron-based catalyst in a suspended bed reactor, a co-catalyst is used together with the catalyst in order to change the catalyst to pyrrhotite (Fe_(1-x)S) which exhibits catalytic activities. As a co-catalyst, sulfur is generally used and added at an amount of approximately 1 to 3 times as much as iron content by atomic ratio. If the co-catalyst is not used, since the function as a haydrocracking catalyst is not demonstrated, a polycondensation reaction occurs and it becomes hard to achieve high yield.

On supplying the above natural limonite iron ore catalyst into a suspended bed reactor, the amount supplied is preferably 0.3-2 mass % as an iron component of the amount of heavy oil supplied (the eighth invention). The reason is as follows. When the amount supplied is less than 0.3 mass %, the amount of coke generation tends to increase rapidly, whereas when the amount supplied is more than 2 mass %, the oil yield is saturated, i.e. no increase thereof in more than 2 mass %, which would tend to become higher costs.

In the present invention, the heavy metal components of heavy oil containing heavy metal components produced in a refining process of crude oil are Ni, V (one or more kinds of Ni or V) and the like. The content of the heavy metal components is not particularly limited. The vacuum residue obtained in a vacuum distillation tower means the distillation residue that atmospheric residue of crude oil is fed to a vacuum distillation tower, distilled under vacuum pressure, and drawn off from the under-part of vacuum distillation tower, namely a vacuum residue of atmospheric residue of crude oil. The atmospheric residue of crude oil means the distillation residue that crude oil is fed to an atmospheric distillation tower, distilled under atmospheric pressure, and drawn off from the under-part of atmospheric distillation tower.

The pressure condition in the vacuum distillation process is generally 10 mmHg to 10 mmHg. In the present invention, the vacuum distillation is carried out at 350° C. or less. For example, the maximum temperature of vacuum distillation tower is controlled in a temperature at 350° C. or less. Namely, the upper limit of the maximum temperature of vacuum distillation tower is regulated at 350° C. The lower limit of the maximum temperature of vacuum distillation tower is neither regulated nor limited, because it depends on the composition of vacuum gas oil fraction to be obtained by vacuum distillation. The maximum temperature of vacuum distillation tower is suitably set by selecting a temperature of 350° C. or less according to the yield of oil content obtained in the hydrocracking reaction step. Ordinarily it is 300 to 350° C.

In a vacuum distillation tower, the highest temperature is the temperature of a liquid-phase part in the under-part of vacuum distillation tower. The highest temperature in a vacuum distillation tower means the temperature of the above liquid-phase part.

Regarding a process of hydrocracking heavy oil of the present invention, one example of more specific embodiment will be described below using a flow chart of FIG. 1. The present invention is not limited to the description shown in FIG. 1.

As shown in FIG. 1, to a slurry preparation tank (1) are added a petroleum heavy oil containing heavy metal components, an iron-based catalyst (for example, natural limonite iron ore catalyst) and sulfur as a co-catalyst to prepare a slurry mixture, then hydrogen gas is added thereto, the slurry is heated by a preheater (2), and supplied into a suspended bed reactor (3), which is a hydrocracking reactor in a reaction step. In this case, as a petroleum heavy oil containing heavy metal components, there are used an atmospheric residue of crude oil (the distillation residue in which crude oil is fed to an atmospheric distillation tower, distilled under atmospheric pressure and drawn off from the under-part of atmospheric distillation tower) and a vacuum residue (the distillation residue in which atmospheric residue is fed to a vacuum distillation tower, distilled under vacuum pressure and drawn off from the under-part of vacuum distillation tower ). The maximum temperature in this vacuum distillation tower is controlled at a temperature of 350° C. or less. A bubble tower type reactor is used as a typical suspended bed reactor. Reaction conditions in the suspended bed reactor (3) are preferably a reaction temperature of 440-450° C.; a reaction pressure of 80-120 kg/cm²; and a reaction time of 1-2 hours. Hydrocracking reaction is conducted in the suspended bed reactor (3) to give a hydrocracking reaction product therein.

The hydrocracking reaction product obtained in the suspended bed reactor (3) is introduced to a first gas-liquid separator (4), and a gas-phase component is separated under conditions of high temperature and high pressure. This gas-phase component is passed to a high pressure/low temperature gas-liquid separator (8) and a gas purification step (9). A part of the gas is used as fuel gas. The rest is used as a recycle gas and a cooling gas for a reactor in the reaction step.

In the above first gas-liquid separator (4), a liquid-phase fluid containing catalyst is separated as well as a gas-phase component. Light fractions in the liquid-phase fluid containing catalyst are separated by a low pressure gas-liquid separator (5) and a reduced pressure gas-liquid separator (6), then a part of the liquid-phase fluid is recycled either to the slurry preparation tank (1) or directly to the suspended bed reactor (3) in the reaction step (the fluid is called recycling fluid A). The rest is transported to a solid-liquid separation step (7), and separated into a liquid fraction, and a solid component mainly containing a catalyst and coke. The liquid fraction is the one mainly having a boiling point of 343° C. or more, and is recycled either to the slurry preparation tank (1) or directly to the suspended bed reactor (3) in the reaction step (the liquid fraction is called recycling fluid B).

Both the recycling fluid A and the recycling fluid B contain heavy residues whose boiling point is 525° C. or more (+525° C.). By recycling them to the reaction step, the re-decomposition of the heavy residues takes place to improve a yield of oil fraction (C5-525° C.). Main difference between the recycling fluid A and the recycling fluid B is that the recycling fluid A contains a catalyst component in the fluid, whereas the recycling fluid B has hardly contains a catalyst component.

in FIG. 1, a pre-heater and a distillation tower are denoted as the numeral (2) and the numeral (10) respectively.

EXAMPLES

Examples of the present invention and Comparative examples will be explained below. The present invention is not limited to the examples, can suitably be modified and carried out to the extent consistent with the spirit of the present invention, and these are all included in the technical scope of the present invention.

Example 1

A process of hydrocracking petroleum heavy oil containing heavy metal components was conducted in the same process as in the above-mentioned FIG. 1.

In this case, a vacuum residue (hereinafter referred to as VR) was used as a petroleum heavy oil containing heavy metal components. Namely, VR was used being obtained in that the atmospheric residue of the fraction composition shown in Table 1 (hereinafter referred to as AR) was fed to a vacuum distillation tower and distilled under the pressure of 10 mmHg at 325° C. of liquid temperature. The maximum temperature in the vacuum distillation tower is 325° C. In Table 1, “wt % on feed AR” means a weight ratio in mass % relative to the amount of AR fed into the vacuum distillation tower.

The kinds and amount of metals contained in AR are as follows:

Ni:15 ppm, V:20 ppm, Ca:3 ppm, Fe:5 ppm

As an iron-based catalyst, a limonite iron ore catalyst containing essentially no iron oxide was used. The limonite iron ore catalyst used was a natural limonite iron ore (Fe content: 53 mass %) mechanically pulverized in a petroleum solvent to have 1 μm in average particle size. The amount of limonite iron ore catalyst added, i.e., the amount supplied was set to be 1 mass % as an iron component of the amount of petroleum heavy oil supplied. The amount of co-catalyst (sulfur) added was set to be 1.2 times the amount of the iron component in atomic ratio.

Reaction conditions in the reaction step, namely, the reaction conditions in the suspended bed reactor (3) employed a reaction pressure of 10 MPa (100 kg/cm²), a reaction temperature of 450° C., and a reaction time of 60 minutes.

A liquid-phase fluid obtained by gas-liquid separation of the reaction product obtained in the reaction step and, a liquid-phase fluid obtained by separating a solid component from the liquid-phase fluid were recycled to the suspended bed reactor (3). Namely, in the first gas-liquid separator (4), a liquid-phase fluid was separated as well as a gas-phase component, light fractions in the liquid-phase fluid were separated by the low pressure gas-liquid separator (5) and reduced pressure gas-liquid separator (6), then a part of the liquid-phase fluid (recycling fluid A) was recycled to the suspended bed reactor (3). The rest was transported to the solid-liquid separation step (7), separated into a solid component and a liquid-phase fluid, and the liquid-phase fluid (recycling fluid B) was recycled to the suspended bed reactor (3). In this time, the amount of liquid-phase fluids (the recycling fluid A and the recycling fluid B) recycled into the suspended bed reactor (3) was set so that the sum of the amount of heavy oil component with a boiling point of 525° C. or more in the recycling fluid A and the amount of heavy oil component with a boiling point of 525° C. or more in the recycling fluid B would be 50 mass % of the amount of VR (vacuum residue) supplied into the suspended bed reactor (3).

As a result, conversion rate of residue was 92%; yield of heavy residue (+525° C.) was 5.8 mass % VR amount (hereinafter, mass % of VR amount is also called % VR); and yield of oil fraction (C5-525° C.) was 84.9% VR (84.9 mass % of VR amount). The conversion rate is obtained by the following formula (1).

Conversion rate of residue (%)=100×[(mass % of +525° C. components in feedstock VR) minus (yield of heavy residue)]/(mass % of +525° C. components in feedstock VR)   Formula (1)

Example 2

The maximum temperature in the vacuum distillation tower was set to be 350° C. Namely, VR was used being obtained in that AR of the fraction composition shown in Table 1 was fed to the vacuum distillation tower and distilled under the pressure of 10 mmHg at 350° C. of liquid temperature. Except for this point, the process of hydrocracking petroleum heavy oil (VR) containing heavy metal components was carried out in the same conditions and the same method as in Example 1.

As a result, conversion rate of residue was 86%; yield of heavy residue (+525° C.) was 11.5% VR (11.5 mass % of VR amount); and yield of oil fraction (C5-525° C.) was 78.5% VR.

Comparative Example 1

The maximum temperature in the vacuum distillation tower was set to be 360° C. Namely, VR was used being obtained in that AR of the fraction composition shown in Table 1 was fed to the vacuum distillation tower and distilled under a pressure of 10 mmHg at 360° C. of liquid temperature. Except for this point, the process of hydrocracking petroleum heavy oil (VR) containing heavy metal components was carried out in the same conditions and the same method as in Example 1.

As a result, conversion rate of residue was 81%; yield of heavy residue (+525° C.) was 15.8% VR; and yield of oil fraction (C5-525° C.) was 73.7% VR.

Comparative Example 2

The maximum temperature in the vacuum distillation tower was set to be 385° C. Namely, VR was used being obtained in that AR of the fraction composition shown in Table 1 was fed to the vacuum distillation tower and distilled under the pressure of 10 mmHg at 385° C. of liquid temperature. Except for this point, the process of hydrocracking petroleum heavy oil (VR) containing heavy metal components was carried out in the same conditions and the same method as in Example 1.

As a result, conversion rate of residue was 81%; yield of heavy residue (+525° C.) was 16.6% VR; and yield of oil fraction (C5-525° C.) was 73.5% VR.

Comparative Example 3

The maximum temperature in the vacuum distillation tower was set to be 360° C. Namely, VR was used being obtained in that AR of the fraction composition shown in Table 1 was fed to the vacuum distillation tower and distilled under the pressure of 10 mmHg at 360° C. of liquid temperature. Also, reaction conditions in the reaction step, that is, the reaction conditions in the suspended bed reactor (3) employed reaction pressure of 15 MPa (150 kg/cm²), reaction temperature of 450° C., and reaction time of 90 minutes. Except for this point, a process of hydrocracking petroleum heavy oil (VR) containing heavy metal components was carried out in the same conditions and the same method as in Example 1.

As a result, conversion rate of residue was 95%, yield of heavy residue (+525° C.) was 4.3% VR; and yield of oil fraction (C5-525° C.) was 80.7% VR.

As is clear from the above Examples 1 to 2, and Comparative examples 1 to 2, as the vacuum distillation temperature (the maximum temperature in the vacuum distillation tower) is raised from 325° C. to 360° C., the reaction efficiency becomes worse, namely, the yield of heavy residue increases, the conversion rate of residue and the yield of oil fraction decrease. The reaction efficiency remains constant in a poor level in the case where the vacuum distillation temperature is 360° C. or more.

The reason is thought as follows. Polycondensation reaction (polymerization reaction) takes place as the temperature in the vacuum distillation operation step rises to produce a lot of heavy materials being hardly decomposed. In order to prevent such deterioration, it is required that the vacuum distillation temperature is controlled at 350° C. or less, and VR obtained from such the condition is used as VR fed to a suspended bed reactor.

As shown in Comparative example 3, when VR obtained in a vacuum distillation temperature of more than 350° C. is used, it is necessary to set a higher reaction pressure and a longer reaction time in order to obtain a relatively high yield of oil fraction of about 80% VR. In this case, plant costs for the hydrocracking process become high.

TABLE 1 Fraction composition, wt % on feed AR 171-232° C. 232-343° C. 343-450° C. 450-525° C. +525° C. Feedstock 0.0 3.0 18.2 24.8 53.9

INDUSTRIAL APPLICABILITY

The process of hydrocracking heavy oil of the present invention makes it possible to give decomposed oil with higher yields and/or milder reaction conditions than the conventionally proposed hydrocracking process in a suspended bed method using an iron-based catalyst when hydrocracking petroleum heavy oil containing heavy metal components produced in a refining process of crude oil into lighter oil. Therefore the present invention is useful since it can be preferably adopted as a process of hydrocracking petroleum heavy oil containing heavy metal components. 

1. A process of hydrocracking heavy oil containing heavy metal components produced in a refining process of crude oil, comprising: a vacuum distillation step to obtain the heavy oil as distillation residue by vacuum distillation; and a reaction step to hydrocrack the heavy oil in the presence of an iron-based catalyst in a suspended bed reactor, wherein the distillation is conducted at 350° C. or less in the vacuum distillation step.
 2. The process of hydrocracking heavy oil according to claim 1, comprising: a recycling step in which a liquid-phase fluid obtained by gas-liquid separation of the reaction products from the reaction step is recycled to the suspended bed reactor; and a recycling step in which after separation of a solid component from the liquid-phase fluid, the resultant fluid is recycled to the suspended bed reactor.
 3. The process of hydrocracking heavy oil according to claim 2, wherein the content of heavy oil components with a boiling point of 525° C. or more in the liquid-phase fluid recycling in the recycling step is 10-100 mass % of the amount of heavy oil supplied into the suspended bed reactor in the reaction step.
 4. The process of hydrocracking heavy oil according to claim 1, wherein the reaction conditions in the reaction step are a reaction pressure of 60-160 kg/cm²; a reaction temperature of 430-455° C.; and a reaction time of 30-180 minutes.
 5. The process of hydrocracking heavy oil according to claim 1, wherein the iron based catalyst is a natural limonite iron ore catalyst.
 6. The process of hydrocracking heavy oil according to claim 1, wherein the iron based catalyst is a natural limonite iron ore catalyst of 2 μm or less in an average particle size being mechanically pulverized in a petroleum solvent.
 7. The process of hydrocracking heavy oil according to claim 5 or claim 6, wherein the natural limonite iron ore catalyst is a natural limonite iron ore catalyst containing essentially no iron oxide.
 8. The process of hydrocracking heavy oil according to claim 5, wherein on supplying the natural limonite iron ore catalyst into the suspended bed reactor, the amount supplied is 0.3-2 mass % as an ion component of the amount of heavy oil supplied. 